Osmosis is a process wherein fluid moves through a semipermeable membrane in an attempt to equalize the chemical potential across the membrane. This process most commonly occurs when fluids having different concentrations of brine, e.g., salt solutions, are placed on opposite sides of the semipermeable membrane. A resulting potential energy, osmotic pressure, is produced that can be converted to mechanical and electrical energy.
U.S. Pat. No. 3,978,344, issued Aug. 31, 1976, to Jellinek, teaches a body of salt water and a body of fresh water, both at ambient pressure, in contact with opposite sides of a semipermeable membrane. Fresh water passes through the membrane with a concomitant build-up of osmotic pressure that causes salt water to be ejected through an orifice and directed against turbine blades to produce mechanical or electrical energy. The salt water and fresh water adjacent the membrane surfaces are simply replaced from adjacent fluid reservoirs.
U.S. Pat. No. 4,283,913, issued Aug. 18, 1981, to Loeb, teaches a low pressure fluid with little or no brine concentration and a pressurized brine solution on opposite side of a semipermeable membrane where the movement of fluid across the membrane forces the brine solution to flow through a turbine to generate mechanical or electrical energy. The depressurized brine solution is then passed to a saturated solar pond where solar energy acts to separate the fluid therein into a vertical gradient of concentrations so that high concentration brine may be removed at one location and low concentration brine at another position. Now the high concentration brine must be pressurized by a relatively high pressure pump for return to the membrane chamber with a concomitant consumption of electrical or mechanical energy and resulting loss of overall process efficiency.
Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.